A kenzan (剣山), also called spiky frog, is a specific device used in the Japanese art of flower arrangement ikebana for fixing the flowers in the container. It consists of a heavy lead plate with erected brass needles where the stipes are fixed.
The name kenzan (剣山) literally means sword mountain. It was introduced by the Moribana style of ikebana.[1]
Another flower holder without spikes but only holes is called shippo dome (七宝留め) and is used by the Saga Go-ryū school and sometimes other schools.